The present disclosure relates to an image forming apparatus which has functions for suctioning toner.
An image forming apparatus such as a printer or a copier often includes a photosensitive drum, which has a circumferential surface to form an electrostatic latent image, a developing device, which supplies toner to the circumferential surface of the photosensitive drum, and a transfer roller, which transfers a toner image formed on the photosensitive drum to a sheet. When the developing device supplies toner to the circumferential surface of the photosensitive drum on which the electrostatic latent image is formed, a toner image is formed on the circumferential surface of the photosensitive drum. During passage of a sheet between the photosensitive drum and the transfer roller, the toner image on the circumferential surface of the photosensitive drum is transferred to the sheet.
The developing device typically includes a developing roller situated near the circumferential surface of the photosensitive drum. Toner on the developing roller is attracted electrostatically to the photosensitive drum. However, all of toner particles do not adhere to the circumferential surface of the photosensitive drum.
While the toner is transferred from the developing roller to the circumferential surface of the photosensitive drum, the photosensitive drum and the developing roller rotate. Toner particles, which fail to adhere to the photosensitive drum, are carried by resultant airflow from the rotations of the photosensitive drum and the developing roller and float inside the image forming apparatus. The floating toner particles may contaminate sheets conveyed in the image forming apparatus.
Various technologies for collecting such toner particles floating in the image forming apparatus have been proposed.
A layout, in which a photosensitive drum, a developing device and a transfer roller come closer together, or another layout to convey sheets vertically contribute significantly to a reduction in size of an image forming apparatus and improvement of image forming speed. Therefore, various devices are often gathered around the photosensitive drum.
If floating toner is suctioned in a direction substantially orthogonal to a sheet conveyance direction, a suction device configured to generate airflow for suctioning the floating toner may be placed more freely in comparison to a suction structure for suctioning the floating toner in a direction substantially parallel to the sheet conveying direction. Accordingly, technologies for suctioning the floating toner in a direction substantially orthogonal to the sheet conveyance direction may be easily applied to the layout in which the aforementioned devices come closer together around the photosensitive drum.
If a suction device connected to a suction port formed on a side surface of a housing of the developing device is used to suction floating toner in a direction substantially orthogonal to a sheet conveyance direction, a strong suction force occurs near a suction port whereas a low suction force occurs at a distant position from the suction port. The floating toner may not be recovered appropriately in such a suction force distribution.
An object of the present disclosure is to provide an image forming apparatus with a recovery structure configured to recover toner by means of suction forces with a small positional fluctuation.